More than half of doctors experience burnout, according to a new study that suggests that may lead to unnecessary and preventable medical errors.

According to research published this month in the medical journal Mayo Clinic Proceedings, doctors who suffer burnout at work are twice as likely to make a major medical error that affects their patient.

Researchers from Stanford University’s School of Medicine surveyed nearly 6,700 doctors in active practice across the U.S. from August 28, 2014, to October 6, 2014. The survey focused on burnout, fatigue, thoughts of suicide, work unit safety grades, and recent medical errors.

About four percent of doctors reported having a poor or failing patient safety grade. An unsafe work environment can triple or quadruple the risk of committing a medical error.

Nearly 20% of doctors reported having made a major medical error within the three months before the survey. Researchers noted that doctors who suffered from burnout were twice as likely to make a medical error than those who were not experiencing burnout.

The doctors who reported errors were 11% more likely to have symptoms of burnout. This held true for fatigue and thoughts of suicide. Doctors who reported errors were 15% more likely to experience fatigue and 7% more likely to have thoughts of suicide.

Burnout not only affected the doctor, but also the hospital and patients as a whole. Medical error rates were triple among hospitals where doctor burnout was a common problem. This was true even if the work environment was thought to be a safe one otherwise.

“In this large national study, physician burnout, fatigue, and work unit safety grades were independently associated with major medical errors,” the researchers wrote.“Interventions to reduce rates of medical errors must address both physician well-being and work unit safety.”

Burnout is quite common among people in high stress professions or professions that have intense interactions with the public, like doctors or law enforcement. Symptoms of burnout include emotional exhaustion and or cynicism. It is often evident with decreased effectiveness in their job.

When doctors experience burnout it is manifested as errors in medical judgment, errors in diagnosing illness, and technical mistakes during procedures. It can also lead to improper medication dosing, improper drug prescribing, or ordering too many or too few lab tests.

These mistakes can cause patients to acquire infections, suffer accidents, or even die prematurely. Other research has tied medical errors to roughly 100,000 to 200,000 patient deaths every year.

Despite how frequently doctor’s may experience burnout, it is a reversible condition. Researchers emphasize the need for the employer to support self-care among doctors, as well as limiting work hours, paperwork overload, and instituting administrative reforms.

Doctors can also be proactive and focus on reducing unnecessary stress, using stress management techniques, and practicing mindfulness training to help prevent burnout or reverse burnout when it happens.